The present invention generally pertains to communication signal processing and is particularly directed to estimating the signal-to-noise ratio (SNR) of a received modulated signal by processing the measured error vector magnitude (EVM).
The EVM is a measure of the tightness of a received signal constellation about a desired constellation point and is thereby an indication of signal fidelity. Many commercial standards require compliance to an EVM requirement since the EVM is much more straightforward to calculate and characterize than a direct Eb/No estimation and since modem imperfections are impossible to separate as a source of EVM or Eb/No degradation. By using use the EVM as a discriminator for the actual modem SNR (Es/No), the received SNR can be estimated quite accurately.
A prior art technique of processing the measured EVM to estimate the SNR is described by D. J. Shin, W. Sung and I. K. Kim, “Simple SNR Methods for QPSK Modulated Short Bursts”, Proc. of IEEE Global Telecommunications Conference, Globecom 2001, San Antonio, Tex., USA, vol. 6, 2001, pp. 3644-3647.